New coolant compositions

Abstract

The present invention relates to novel coolant compositions based on freezing point-lowering liquids as main constituent, specific sulphur-comprising organic compounds as corrosion inhibitors, and also further corrosion inhibitors which are different therefrom.

Description

[0001] New Coolant Compositions

[0002] Description

[0003] The present invention relates to novel coolant compositions based on freezing point-lowering liquids as main constituent, specific sulphur-comprising organic compounds as corrosion inhibitors, and also further corrosion inhibitors which are different therefrom.

[0004] Coolant compositions for the cooling apparatuses (which are usually configured as cooling circuits) of internal combustion engines of, for example, automobiles usually comprise alkylene glycols such as monoethylene glycol or monopropylene glycol, optionally in admixture with glycerol, as antifreeze component which lowers the freezing point of the coolant composition. Apart from further components such as antifoams, dyes or bitter substances, corrosion inhibitors, in particular, are comprised.

[0005] Especially in modern internal combustion engines, temperatures which place severe demands on the materials used are reached. Any type and any extent of corrosion represent a potential risk factor which can lead to shortening of the life of the engine and to a decrease in reliability. Furthermore, a number of different materials, for example cast iron, copper, brass, soft solder, steel and also aluminium, aluminium alloys and magnesium alloys, are increasingly being used in modern engines. This plurality of metallic materials additionally results in potential corrosion problems, in particular at the places where different metals are in contact with one another. Various types of corrosion such as pit corrosion, crevice corrosion, erosion or cavitation can occur comparatively easily at such places in particular. The coolant compositions likewise have to be compatible with nonmetallic constituents of the cooling apparatuses, for example elastomers and plastics from hose connections or seals, and must not change these. Furthermore, the type of coolant composition is of critical importance for heat transfer in modern internal combustion engines.

[0006] For some time, the cooling apparatus or cooling circuits for internal combustion engines which are usually used in vehicle and automobile construction but also for stationary engines have been made predominantly or solely of aluminium or aluminium alloys. Specific soldering processes, for example soldering under a protective gas atmosphere, are used here. In such soldering processes, the concomitant use of a flux is necessary. Here, potassium fluoroaluminates are usually used as flux, for example a mixture of KAIF4, K2AIF5 and K3AI Fe (for example commercially available under the name Nocolok®).

[0007] Part of the fluxes mentioned remains on the surface of the cooling apparatus after the soldering operation. These flux residues in the cooling apparatus lead more or less quickly to precipitation of aluminium hydroxide gels and thus to sludge formation in the cooling circuit after introduction of aqueous coolant compositions and operation of the engine due to a chain of chemical reactions, which are in equilibrium with one another, with the water and the constituents of the aqueous coolant compositions. This greatly restricts the effectiveness of heat removal from the engine and as a consequence also the functions of the heat exchange for the heating system, cooling of the air supply and gearbox oil cooling. In addition, the presence of aluminium hydroxide gels has an adverse effect on the corrosion protection provided by the coolant because the corrosion protection action is considerably reduced as a result of adsorption of the corrosion inhibitors on the aluminium hydroxide gels. Therefore, there is a demand for coolant compositions which have a high tolerance to residues of fluoroaluminate fluxes in soldered aluminium radiators, i.e. which no longer tends, or tends to a significantly less extent, to form precipitates of aluminium hydroxide gels and formation of sludge in the cooling circuit and thus makes more effective corrosion protection possible.

[0008] EP 2956520 B1 discloses coolant concentrates comprising - inter alia - certain 2-thiothiazole derivatives bearing a carboxyalkyl radical.

[0009] Such sulphur-containing inhibitors provide excellent inhibition of aluminium corrosion even in the presence of potassium fluoroaluminates.

[0010] However, it is a disadvantage that the coolants according to EP 2956520 B1 exhibit a high electrical conductivity.

[0011] A low electrical conductivity is worth striving for to make coolants suitable for application in cooling systems of vehicles with electric engines, fuel cells or hybrid engines, since a high electrical conductivity may lead to a short circuit in case the battery is harmed e.g. in an accident.

[0012] Therefore, it was an object of the present invention to provide coolant compositions with a lower electrical conductivity than the coolants according to EP 2956520 B1 but maintaining the corrosion inhibition activity of those coolants, also in the presence of fluoroaluminates.

[0013] The coolants according to the invention have to fulfil the general requirements according to ASTM D3306, inter alia the corrosion test according to ASTM D4340 as well as ASTM D1384.

[0014] The object was achieved by coolants, comprising

[0015] (A) at least one antifreezing agent selected from the group consisting of 1 ,2-ethylene glycol, 1 ,2-propylene glycol, 1,3- propylene glycol, glycerol, dimers, trimers or oligomers thereof, and mono- or dialkyl ethers thereof

[0016] (B) water

[0017] (C1 ) at least one 2-thiothiazole of the general formula (I) where the variable R1 is a carboxyalkyl radical of the formula -(CmH2m)-C00X, where m is from 1 to 4 and X is hydrogen, an alkali metal cation, an ammonium cation or a substituted ammonium cation, and the variables R2 and R3 are each, independently of one another, hydrogen or a Ci-C4-alky I group, where R2 and R3 together with the two ring carbon atoms of the thiazole ring to which they are attached may also form a five- or six-membered saturated or unsaturated ring,

[0018] (C2) optionally at least one azol derivative different from (C1 ),

[0019] (D) at least one inorganic salt as further corrosion inhibitor selected from the group consisting of molybdates, borates, vanadates, tungstates, and antimonates,

[0020] (E) optionally at least one inorganic phosphate salt as further corrosion inhibitor,

[0021] (F) at least one aliphatic, cycloaliphatic or aromatic monocarboxylic, dicarboxylic or tricarboxylic acid in the form of alkali metal, ammonium or substituted ammonium salts thereof having from 3 to 21 carbon atoms in the acid part, and

[0022] (G) at least on alkylamine of the general formula (II) where

[0023] R4is an organic radical having from 6 to 10 carbon atoms, in particular an alkyl or alkenyl radical having from 6 to 10 carbon atoms, preferably from 7 to 9 and particularly preferably 8 carbon atoms, p and q are each, independently of one another, a positive integer from 1 to 20, preferably from 1 to 15, particularly preferably from 1 to 10, very particularly preferably from 1 to 5 and in particular from 1 to 3, and each Xj for i = 1 to p and 1 to q is selected independently from the group consisting of -CH2-CH2-O-, -CH2-CH(CH3)-O-, -CH(CH3)-CH2-O-, -CH2-C(CH3)2-O-, -C(CH3)2-CH2-O-, -CH2-CH(C2H5)-O-, -CH(C2H5)-CH2-O-, -CH(CH3)-CH(CH3)-O-, -CH2-CH2-CH2-O- and -CH2-CH2-CH2-CH2-O-, preferably selected from the group consisting of -CH2-CH2-O-, -CH2-CH(CH3)-O- and -CH(CH3)-CH2-O-, with particular preference being given to -CH2-CH2-O-.

[0024] Target electrical conductivity according to ASTM D 1125 at 25 °C of such coolants (as 50% agueous solution) is from 150 to 3000 piS / cm, preferably from 175 to 2750, more preferably from 200 to 2500 piS / cm.

[0025] Such electrical conductivity makes the coolants according to the present invention suitable not only for cooling systems of vehicles with internal combustion engines, but also for cooling systems of vehicles with electric engines, hybrid engines with a combination of combustion engines with electric engines.

[0026] Suitable electric vehicles are fully electric vehicles and hybrid electric vehicles. An electric vehicle usually comprises a rotary electric machine and an electric power storage device configured to store electric power that is used to drive the rotary electric machine. A hybrid electric vehicle usually travels by using power of a rotary electric machine and a combustion engine.

[0027] Suitable hybrid electric vehicles are full hybrid (also called strong hybrid), plug-in hybrid (also called PHEV) electric vehicles, or range extended electric vehicles (also called REEV). A full hybrid electric vehicle is typically a vehicle that can run only on a combustion engine, only on an electric motor, or a combination of both. A plug-in hybrid electric vehicle is typically a hybrid electric vehicle with rechargeable batteries that can be restored to full charge by connecting a plug to an external electric power source.

[0028] Preferred electric vehicles are battery electric vehicles (also called BEV). A BEV is typically a type of electric vehicle that uses chemical energy stored in rechargeable battery packs, and uses electric motors and motor controllers instead of internal combustion engines for propulsion.

[0029] The term "vehicle" refers to any mobile or stationary platform, wherein mobile platforms are preferred. In particular vehicles are selected from a passenger vehicle, a light-duty or heavy-duty truck, a utility vehicle, an agricultural vehicle, an industrial or warehouse vehicle, or a recreational off-road vehicle.

[0030] Thus, it is one advantage of the coolants according to the present invention that the car manufacturers do not have to stock different coolants for vehicles with combustion engines and electric engines but can use one type of coolant for all vehicles.

[0031] The compounds of the coolants according to the invention are described in more detail:

[0032] (A) Antifreezing agent As antifreezing agent (A) according to the present invention one or more compounds selected from the group consisting of 1 ,2-ethylene glycol, 1,2-propylene glycol, 1 ,3-propylene glycol, glycerol or dimers, trimers or oligomers thereof or mono- or dialkyl ethers thereof are used.

[0033] Preference is given to 1 ,2-ethylene glycol or 1,2-propylene glycol or dimers, trimers or oligomers thereof or mono- or dialkyl ethers thereof.

[0034] Special preference is given to 1 ,2-ethylene glycol or 1 ,2-propylene glycol, especially 1 ,2-ethylene glycol.

[0035] Preferably 1,2-propylene glycol and its derivatives is used. Derivatives of 1,2-propylene glycol may be poly- and oligomers as well as mono- or dialkyl ethers of 1 ,2-propylene glycol, its poly- and oligomers.

[0036] More preferably 1 ,2-ethylene glycol and its derivatives is used. Derivatives of 1 ,2-ethylene glycol may be poly- and oligomers as well as mono- or dialkyl ethers of 1 ,2-ethylene glycol, its poly- and oligomers. Examples are diethylene glycol, triethylene glycol, diethylene glycol mono C1-C4 alkyl ether, and triethylene glycol mono C1-C4 alkyl ether, even more preferably 1 ,2-ethylene glycol, diethylene glycol, and triethylene glycol, most preferably 1 ,2-ethylene glycol or diethylene glycol, and especially 1 ,2-ethylene glycol.

[0037] Dimers, trimers or oligomers of the alkylene glycols mentioned are di alkylene glycols, tri alkylene glycols, tetra alkylene glycols as well as higher homologues thereof up to a molecular weight of 598 g / mol.

[0038] Preference is given to the monomeric alkylene glycols and their dimers or trimers, more preferred are the monomeric alkylene glycols and their dimers, special preference is given to the monomeric alkylene glycols.

[0039] Mono- or dialkyl ethers of the above-mentioned alkylene glycols and their poly- and oligomers are preferably mono- or di-Ci- to C4-alky I ethers, more preferably mono-Ci- to C4-alky I ethers, even more preferably methyl-, ethyl- or n- butyl ethers, especially mono- methyl-, ethyl- or n-butyl ethers.

[0040] In the context of the present text the phrase "Ci- to C4-alkyl" stands for methyl, ethyl, n-propyl, iso-propyl, n-butyl, isobutyl, sec-butyl and tert-butyl, preferably methyl, ethyl, n-propyl, n-butyl, iso-butyl, and tert-butyl, more preferably methyl, ethyl, and n-butyl.

[0041] Preferably compounds (A) are selected from the group consisting of monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and mixtures thereof, 1 ,3-propanediol, higher poly alkylene glycols, alkylene glycol ethers, for example monoethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, monoethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, monoethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether or glycerol, in each case either alone or as mixtures thereof.

[0042] Preferably compound (A) is 1,2-ethylene glycol or 1 ,2-propylene glycol, especially 1,2-ethylene glycol.

[0043] (B) Water

[0044] Water used for the coolants according to the present invention should be ion-free, designating water with a neutral pH-value and comprising essentially no further ions than those hydroxide ions and hydronium ions out of the autoprotolysis of water at the respective temperature.

[0045] The electrical conductivity (throughout this text determined according to ASTM D 1125) at 25 °C of the ion-free water used should preferably not exceed 5 piS / cm, more preferably not more than 3, even more preferably not more than 2, and especially not more than 1 piS / cm.

[0046] The ion-free water used can be pure distilled or twice-distilled water or water which has been deionized, for example by ion exchange, preferably by ion exchange of at least its cations, more preferably by ion exchange of both cations and anions.

[0047] (C1) 2-Thiothiazole

[0048] The at least one 2-thiothiazole (C1) of the general formula (I) where the variable R1 is a carboxyalkyl radical of the formula -(CmH2m)-C00X, where m is from 1 to 4 and X is hydrogen, an alkali metal cation, an ammonium cation or a substituted ammonium cation, and the variables R2 and R3 are each, independently of one another, hydrogen or a Ci-C4-alkyl group, where R2 and R3 together with the two ring carbon atoms of the thiazole ring to which they are attached may also form a five- or six-membered saturated or unsaturated ring.

[0049] Preference is given to the benzothiazoles of the general formula (III) where the variable R is hydrogen or a Ci-Cio-alkyl radical, in particular methyl or ethyl, and the variable R' is -S-R1.

[0050] Preferred are (2-benzothiazylthio)acetic acid (R = H, R' = -S-CH2-COOH) or (2-benzothiazylthio) propionic acid (R = H, R' = -S-CH2-CH2-COOH), especially (2-benzothiazylthio)acetic acid.

[0051] (C2) Azol derivative different from (C1)

[0052] The coolants according to the invention may optionally further comprise at least one azol derivative (C2) different from (C1).

[0053] Azole derivatives in the context of the present description mean five-membered heterocyclic compounds having 2 or 3 heteroatoms from the group consisting of nitrogen and sulphur and comprise no or at most one sulphur atom and can bear an aromatic or saturated six-membered fused-on ring.

[0054] These five-membered heterocyclic compounds (azole derivatives) usually contain two N atoms and no S atom, 3 N atoms and no S atom or one N atom and one S atom as heteroatoms.

[0055] Preferred groups of the specified azole derivatives are annellated imidazoles and annel lated 1 , 2, 3-tri azoles of the general formula

[0056] (1) or (2) where the variable R is hydrogen or a Ci-Cio-alkyl radical, in particular methyl or ethyl, and the variable X is a nitrogen atom or the C-H group.

[0057] Typical and preferred examples of azole derivatives of the general formula (1) are benzimidazole (X = C-H, R = H), benzotriazoles (X = N, R = H) and tolutriazole (tolyltriazole) (X = N, R = CH3). A typical example of an azole derivative of the general formula (2) is hydrogenated 1 ,2,3-tolutriazole (tolyltriazole) (X = N, R = CH3).

[0058] A further preferred group of the specified azole derivatives is benzothiazoles of the general formula (3) where the variable R is as defined above and the variable R' is hydrogen, a Ci-Cio-alkyl radical, in particular methyl or ethyl, or in particular a mercapto group (- SH). A typical example of an azole derivative of the general formula (3) is 2-mercaptobenzothiazole.

[0059] Further suitable azole derivatives are non-annellated azole derivatives of the general formula (4)

[0060] (4) where the variables X and Y together are two nitrogen atoms or one nitrogen atom and a C-H group, for example 1 H-1 ,2,4-triazole (X = Y = N) or preferably imidazole (X = N, Y = C-H).

[0061] For the purposes of the present invention, benzimidazole, benzotriazole, tolutriazole, hydrogenated tolutriazole or mixtures thereof, in particular benzotriazole or tolutriazole, are very particularly preferred as azole derivatives.

[0062] (D) Inorganic salt

[0063] The inorganic salt (D) is at least one inorganic salt as further corrosion inhibitor selected from the group consisting of molybdates, borates, vanadates, tungstates, and antimonates, preferably selected from the group consisting of molybdates, borates, and vanadates, more preferably selected from the group consisting of molybdates, borates, and vanadates, even more preferably are molybdates.

[0064] As molybdate it is usual to use the alkali metal, ammonium or substituted ammonium salts of molybdic acid H2MOO4 or the acid itself, where alkali metal, ammonium or substituted ammonium salts have the meanings indicated above. Typical representatives of such molybdates (C) are sodium molybdate and potassium molybdate.

[0065] Borates are usually used in the form of sodium tetraborate (borax).

[0066] In a preferred embodiment no silicon-containing species are present in the coolant according to the invention. This refers to both inorganic silicates as well as organic silicon-containing compounds, such as esters of orthosilicic acid.

[0067] (E) Phosphate

[0068] As optional compound (D) at least one inorganic phosphate salt is used as further corrosion inhibitor.

[0069] It is usual to use the alkali metal, ammonium or substituted ammonium salts of orthophosphoric acid H3PO4 or the acid itself, where alkali metal, ammonium or substituted ammonium salts have the meanings indicated above. However, the component (E) will generally be present entirely or predominantly in salt form in the coolant of the invention which normally has a pH of from 4 to 11 , in particular from 7 to 11 . When free orthophosphoric acid is used, this is usually converted by means of sodium or potassium hydroxide, ammonia or appropriate amines into the desired salts. Further suitable components (E) are alkali metal, ammonium or substituted ammonium salts of diphosphoric acid, of metaphosphoric acids, of pyrophosphoric acids and / or of polyphosphoric acids or the acids themselves, where alkali metal, ammonium or substituted ammonium salts have the meanings indicated above. It is also possible to use mixtures of the salts and / or acids mentioned. Typical representatives of such phosphates (E) are sodium dihydrogenphosphate, disodium hydrogenphosphate, trisodium phosphate, sodium diphosphate, tetrasodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate and the analogous potassium salts.

[0070] (F) Carboxylic acids

[0071] The coolants according to the present invention further comprise at least one aliphatic, cycloaliphatic or aromatic monocarboxylic (F1), dicarboxylic or tricarboxylic (F2) acid in the form of alkali metal, ammonium or substituted ammonium salts thereof having from 3 to 21 carbon atoms in the acid part.

[0072] (F1) aliphatic, cycloaliphatic or aromatic, preferably aliphatic or aromatic, and very preferably aliphatic monocarboxylic acids having in each case from 3 to 16 carbon atoms in the form of their alkali metal, ammonium or substituted ammonium salts; (F2) aliphatic or aromatic dicarboxylic or tricarboxylic acids, preferably dicarboxylic acids, even more preferably aliphatic dicarboxylic acids having in each case from 3 to 21 carbon atoms in the form of their alkali metal, ammonium or substituted ammonium salts.

[0073] Possible linear or branched aliphatic or cycloaliphatic, preferably aliphatic monocarboxylic acids of group (F1) are, for example, propionic acid, pentanoic acid, hexanoic acid, cyclohexyl acetic acid, octanoic acid, 2-ethylhexanoic acid, n- nonanoic acid (pelargonic acid), isononanoic acid, decanoic acid, neodecanoic acid, undecanoic acid or dodecanoic acid. Suitable aromatic monocarboxylic acids of group (F1) are in particular benzoic acid and also, for example, Ci- Cs-alkylbenzoic acids such as o-, m- or p-methylbenzoic acid or p-tert-butylbenzoic acid, hydroxyl-comprising aromatic monocarboxylic acids such as o-, m- or p-hydroxybenzoic acid or p-(hydroxymethyl)benzoic acid or halobenzo- ic acids such as o-, m- or p-fluorobenzoic acid.

[0074] As used herein, isononanoic acid refers to one or more branched-chain aliphatic carboxylic acids with 9 carbon atoms. Embodiments of isononanoic acid used in the engine coolant composition may include 7-methyloctanoic acid (e.g., CAS Nos. 693-19-6 and 26896-18-4), 6,6-dimethylheptanoic acid (e.g., CAS No. 15898-92-7), 3,5,5- trimethylhexanoic acid (e.g., CAS No. 3302-10-1), 3,4,5-trimethylhexanoic acid, 2,5,5-trimethylhexanoic acid, 2, 2,4,4- tetramethylpentanoic acid (e.g., CAS No. 3302-12-3) and combinations thereof. In a preferred embodiment, isononanoic acid has as its main component greater than 90% of one of 7-methyloctanoic acid, 6,6-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, 3,4,5-trimethylhexanoic acid, 2,5,5-trimethylhexanoic acid, and 2, 2,4,4- tetramethylpentanoic acid. The balance of the isononanoic acid may include other nine carbon carboxylic acid isomers and minor amounts of one or more contaminants. In a preferred embodiment, the isononanoic acid has as its main component greater than 90% of 3,5,5-trimethylhexanoic acid and even more preferably, the main component is greater than 95% 3,5,5-trimethylhexanoic acid.

[0075] Preferred are 2-ethylhexanoic acid, n-nonanoic acid (pelargonic acid), and isononanoic acid

[0076] Typical examples of dicarboxylic or tricarboxylic acids, preferably dicarboxylic acids, more preferably aliphatic dicarboxylic acids of group (F2) are malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid (decanedioic acid), undecanedioic acid, dodecanedioic acid, cyclopentadienedicarboxylic acid, terephthalic acid, phthalic acid and triazinetriiminocarboxylic acids such as 6,6',6"-(1,3,5-triazine-2,4,6- triyltriimino)trihexanoic acid. Among these the aliphatic individuals are especially preferred.

[0077] Preferred are adipic acid and sebacic acid (decanedioic acid).

[0078] The abovementioned carboxylic acids (F) are usually present entirely or predominantly as alkali metal, ammonium or substituted ammonium salts, as defined above, even when they are to have been added as free acids in the production of the antifreeze concentrate of the invention since the concentrate normally has a pH of from 4 to 11 , in particu- lar from 7 to 11, more preferably from 7 to 10, even more preferably from 7.5 to 9.5. Components (F) used as free carboxylic acids are usually converted by means of sodium or potassium hydroxide, ammonia or appropriate amines into the desired salts, preferably by means of sodium or potassium hydroxide.

[0079] In one embodiment at least one aliphatic monocarboxylic acid is present in the coolants according to the invention.

[0080] In another embodiment at least one aliphatic dicarboxylic acid is present in the coolants according to the invention.

[0081] In a preferred embodiment a mixture of at least one aliphatic mono- and at least one aliphatic dicarboxylic acid is present in the coolants according to the invention.

[0082] (G) Alkylamine

[0083] A further constituent is at least on alkylamine of the general formula (II) where

[0084] R4is an organic radical having from 6 to 10 carbon atoms, in particular an alkyl or alkenyl radical having from 6 to 10 carbon atoms, preferably from 7 to 9 and particularly preferably 8 carbon atoms, p and q are each, independently of one another, a positive integer from 1 to 20, preferably from 1 to 15, particularly preferably from 1 to 10, very particularly preferably from 1 to 5, in particular from 1 to 3, especially 1 to 2, and even 1 , and each Xj for i = 1 to p and 1 to q is selected independently from the group consisting of -CH2-CH2-O-, -CH2-CH(CH3)-O-, -CH(CH3)-CH2-O-, -CH2-C(CH3)2-O-, -C(CH3)2-CH2-O-, -CH2-CH(C2H5)-O-, -CH(C2H5)-CH2-O-, -CH(CH3)-CH(CH3)-O-, -CH2-CH2-CH2-O- and -CH2-CH2-CH2-CH2-O-, preferably selected from the group consisting of -CH2-CH2-O-, -CH2-CH(CH3)-O- and -CH(CH3)-CH2-O-, with particular preference being given to -CH2-CH2-O-.

[0085] It should be noted that the compounds of the formula (II) are usually reaction mixtures having a distribution of the product composition which depends on the reaction conditions. Thus, the length of the chain -[- -]- is subject to a distribution about a statistical average, so that the values for p and q can be distributed about a statistical average. Thus, the value for p and q for each individual compound of the formula (II) is a positive integer, but for the reaction mixture can on statistical average also have nonintegral values.

[0086] In the compounds of the formula (II), the structural element R4-N< is preferably derived from fatty amines which are preferably obtainable by hydrogenation and amination of fatty acids and esters, particularly preferably by hydrogenation and amination of the abovementioned fatty acids or amination of the abovementioned fatty alcohols. What has been said with regard to the fatty alcohols also applies analogously to the fatty amines.

[0087] As radicals R4, preference is given to alkyl radicals over alkenyl radicals.

[0088] In a preferred embodiment, the fatty amines are n-hexylamine, 2-methylpentylamine, n-heptylamine, 2-heptylamine, isoheptylamine, 1 -methylhexylamine, n-octylamine, 2-ethylhexylamine, 2-ami nooctane, 6-methyl-2-heptylamine, n- nonylamine, isononylamine, n-decylamine and 2-propylheptylamine or mixtures thereof.

[0089] Particular preference is given to n-hexylamine, n-octylamine, 2-ethylhexylamine and n-decylamine, with n-octylamine and 2-ethylhexylamine, in particular n-octylamine, being particularly preferred.

[0090] Particular mention may be made of two-fold, three-fold and four-fold ethoxylated n-octylamine and also two-fold, three-fold and four-fold ethoxylated n-hexylamine.

[0091] In the alkoxylated amines of the general formula (II), the degree of alkoxy lation refers to the sum (p + q), i.e. to the average total number of alkoxy lation units per molecule of amine.

[0092] The compounds (II) are preferably obtainable by reacting the corresponding amines R4-NH2 with alkylene oxides to the desired average statistical degree of alkoxylation, preferably under basic conditions. This is particularly preferred when the structural unit Xi is derived from ethylene oxide or propylene oxide, preferably from ethylene oxide.

[0093] (H) Other additives

[0094] It is possible to add further typical coolant additives to the coolants of the present invention.

[0095] As further customary assistants, the inventive coolant may also comprise, in customary small amounts, defoamers (generally in amounts of from 0.002 to 0.008% by weight) and, for reasons of hygiene and safety in the event that it is swallowed, and bitter substances (for example of the denatonium benzoate type, generally in amounts of from 0.005 to 0.02% by weight).

[0096] Furthermore, the coolants may comprise dyes (generally in amounts of from 0.001 to 0.005% by weight) and hard water stabilisers (generally in amounts of from 0.1 to 0.5% by weight), e.g. based on polyacrylic acid, polymaleic acid, acrylic acid-maleic acid copolymers, polyvinylpyrrolidone, polyvinylimidazole, vinylpyrrolidone-vinylimidazole copolymers and / or copolymers of unsaturated carboxylic acids and olefins.

[0097] Composition

[0098] The composition of the coolants according to present invention are as follows:

[0099] (A) 45 to 65 wt% of at least one antifreezing agent, preferably 50 to 60, more preferably 50 to 55 wt%

[0100] (B) 30 to 50 wt% water, preferably 35 to 50, more preferably 40 to 50 wt%,

[0101] (C1) 0.01 to 0.5 wt% of at least one 2-thiothiazole of the general formula (I), preferably 0.02 to 0.4, more preferably 0.05 to 0.2 wt%,

[0102] (C2) 0 to 0.75 wt% of at least one azol derivative different from (C 1 ), preferably 0.02 to 0.5, more preferably 0.05 to 0.25 wt%,

[0103] (D) 0.01 to 0.75 wt% of at least one inorganic salt as further corrosion inhibitor, preferably 0.02 to 0.5, more preferably 0.05 to 0.3 wt%,

[0104] (E) 0 to 2 wt% at least one inorganic phosphate salt, preferably 0.01 to 1.5, more preferably 0.01 to 1.0 wt%,

[0105] (F) 0.1 to 2 wt% at least one aliphatic, cycloaliphatic or aromatic monocarboxylic, dicarboxylic or tricarboxylic acid, preferably 0.5 to 1.75, more preferably 1.0 to 1.5 wt%, and

[0106] (G) 0.5 to 2.0 wt% of at least on alkylamine of the general formula (II), preferably 0.75 to 1 .75, more preferably 1 .0 to

[0107] 1.75 wt%,

[0108] (H) optionally other additives selected from the group consisting of defoamers, bitter substances, and hard water stabilisers, with the proviso that the sum of all components always add up to 100 wt%.

[0109] The coolants as described are usually destined for use at the final user, i.e. for refilling of the cooling system of vehicles.

[0110] Coolants usually are obtained from coolant concentrates by dilution with water (B). Therefore, another subject matter of the present invention are coolant concentrates which usually contain little or no water (B):

[0111] The composition of the coolant concentrates according to present invention are as follows:

[0112] (A) 80 to 95 wt% of at least one antifreezing agent, preferably 80 to 90, more preferably 85 to 95 wt%

[0113] (B) 0 to 10 wt% water, preferably 0 to 8, more preferably 0 to 5 wt%,

[0114] (C1) 0.02 to 1.0 wt% of at least one 2-thiothiazole of the general formula (I), preferably 0.04 to 0.8, more preferably 0.1 to 0.4 wt%, (02) 0 to 1.5 wt% of at least one azol derivative different from (01), preferably 0.04 to 1.0, more preferably 0.1 to 0.5 wt%,

[0115] (D) 0.02 to 1.5 wt% of at least one inorganic salt as further corrosion inhibitor, preferably 0.2 to 1.0, more preferably 0.1 to 0.6 wt%,

[0116] (E) 0 to 4.0 wt% at least one inorganic phosphate salt, preferably 0.02 to 3.0, more preferably 0.02 to 2.0 wt%,

[0117] (F) 0.2 to 4 wt% at least one aliphatic, cycloaliphatic or aromatic monocarboxylic, dicarboxylic or tricarboxylic acid, preferably 1.0 to 3.5, more preferably 2.0 to 3.0 wt%, and

[0118] (G) 1.0 to 4.0 wt% of at least on alkylamine of the general formula (II), preferably 1.5 to 3.5, more preferably 2.0 to 3.5 wt%, with the proviso that the sum of all components always add up to 100 wt%.

[0119] Coolants are usually obtained from the concentrates by dilution with water (B) in the ratio 1 :0.75 to 1 :1.5 (v / v).

[0120] A further embodiment of the present invention are coolant super concentrates. Coolant concentrates usually are obtained from coolant super concentrates by dilution with the glycol (A), respectively coolants may be obtained from coolant super concentrates by dilution with the glycol (A) and water (B). Hence, the coolant super concentrates usually contain little or no water (B) and less glycol than the concentrates. In the concentrates or super concentrates glycol (A) acts as a solvent for the other constituents and, therefore, may be present in higher amounts.

[0121] The composition of the coolant super concentrates according to present invention are as follows:

[0122] (A) 20 to 90 wt% of at least one antifreezing agent, preferably 30 to 85, more preferably 40 to 80 wt%

[0123] (B) 0 to 10 wt% water, preferably 0 to 8, more preferably 0 to 5 wt%,

[0124] (C1) 0.03 to 1.5 wt% of at least one 2-thiothiazole of the general formula (I), preferably 0.06 to 1.4, more preferably 0.15 to 0.6 wt%,

[0125] (C2) 0 to 2.25 wt% of at least one azol derivative different from (C1), preferably 0.06 to 1.5, more preferably 0.15 to 0.75 wt%,

[0126] (D) 0.03 to 2.25 wt% of at least one inorganic salt as further corrosion inhibitor, preferably 0.3 to 1.5, more preferably 0.15 to 0.9 wt%,

[0127] (E) 0 to 6.0 wt% at least one inorganic phosphate salt, preferably 0.03 to 4.5, more preferably 0.03 to 3.0 wt%,

[0128] (F) 0.3 to 6 wt% at least one aliphatic, cycloaliphatic or aromatic monocarboxylic, dicarboxylic or tricarboxylic acid, preferably 1.5 to 5.25, more preferably 3.0 to 4.5 wt%, and

[0129] (G) 1.5 to 6.0 wt% of at least on alkylamine of the general formula (II), preferably 2.25 to 5.25, more preferably 3.0 to 5.25 wt%, with the proviso that the sum of all components always add up to 100 wt%.

[0130] It is an advantage of the present coolants that they exhibit not only a high tolerance to residues of fluoroaluminate fluxes in soldered aluminium radiators but also a high inhibition of corrosion, especially corrosion of ferrous- and aluminium-containing alloys, and non-ferrous-alloys.

[0131] Therefore, another aspect of the present invention is the use of the coolants according to the present invention in cooling systems which are at least partly, preferably predominantly or solely made of aluminium or aluminium alloys.

[0132] The electrical conductivity is reduced compared to the coolants according to EP 2956520 B1 with simultaneous retention of their anti-corrosion activity.

[0133] Examples

[0134] If not mentioned otherwise electrical conductivity was determined according to ASTM D 1125 at 25 °C in piS / cm throughout the text.

[0135] Corrosion tests according to ASTM D 1384 using GAISi6Cu4 specimen were conducted for 336 hours (14 days) at 88 °C, corrosion rate given in mg / cm2.

[0136] The corrosion test in accordance with ASTM D 4340 is a standard test that serves to determine the corrosion susceptibility of aluminium or aluminium alloys in cooling apparatuses for internal combustion engines. The standard apparatus used for this purpose simulates the aluminum-comprising hot inner surface of a cooling circuit of an internal combustion engine. An aluminium test plate is heated from below while its upper surface is in contact with the cooling fluid to be tested. The test temperature is 135°C. After conclusion of the test after the set-down test time of 168 hours, the plate is assessed visually for corrosion and the weight change (after pickling) is determined by weighing. Standard coupon is GAISi6Cu4, corrosion rate is given in mg / cm2.

[0137] Electrical conductivity was measured as 50% aqueous solution.

[0138] Corrosion test according to ASTM D1384 was carried out in 33.3% aqueous solution for 336 h in the presence of "corrosive water" according to test procedure

[0139] Corrosion test according to ASTM D4340 was carried out in 25% aqueous solution for 168 h, in the presence of "corrosive water" according to test procedure

[0140] As comparative example a coolant similar to KM3 of EP 2956520 B1 without tetraalkoxysilane was used as Comparative Example 1 .

[0141] The coolants further comprise commercially available defoamer, hard water stabiliser, dyes, and bitter substance.

[0142] *) As 50% aqueous solution.

[0143] As target it was set to reach an electrical conductivity of 2400 piS / cm for the 50% aqueous solution the coolant ac- cording to Comparative Example 1 was diluted with monoethylene glycol until the desired electrical conductivity was reached (about 35 vol% Comparative Example 1 diluted with 65 vol% monoethylene glycol.

[0144] It can easily be seen that simple dilution of the coolant of Comparative Example 1 with monoethylene glycol to reach the desired electrical conductivity leads to a coolant with insufficient corrosion inhibition.

[0145] Therefore, the amount of corrosion inhibitors (sebacic acid, tolutriazole, and (2-benzothiazyl thio) acetic acid) was increased and n-octyldiethanolamine added:

[0146]

[0147] It can easily be seen that the corrosion inhibition is improved with higher amounts of n-octyldiethanolamine without simultaneously significantly affecting the electrical conductivity.

[0148] *) Duration of corrosion test according to ASTM D13847 days only It can easily be seen that even without phosphate good corrosion resistance can be achieved, however, phosphate is advantageous even in small amounts.

Claims

Claims1. Coolants, comprising(A) at least one antifreezing agent selected from the group consisting of 1 ,2-ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, glycerol, dimers, trimers or oligomers thereof, and mono- or dialkyl ethers thereof(B) water(C1) at least one 2-thiothiazole of the general formula (I)where the variable R1 is a carboxyalkyl radical of the formula -(CmH2m)-C00X, where m is from 1 to 4 and X is hydrogen, an alkali metal cation, an ammonium cation or a substituted ammonium cation, and the variables R2 and R3 are each, independently of one another, hydrogen or a Ci-C4-alkyl group, where R2 and R3 together with the two ring carbon atoms of the thiazole ring to which they are attached may also form a five- or six-membered saturated or unsaturated ring,(C2) optionally at least one azol derivative different from (C1 ),(D) at least one inorganic salt as further corrosion inhibitor selected from the group consisting of molybdates, borates, vanadates, tungstates, and antimonates,(E) optionally at least one inorganic phosphate salt as further corrosion inhibitor,(F) at least one aliphatic, cycloaliphatic or aromatic monocarboxylic, dicarboxylic or tricarboxylic acid in the form of alkali metal, ammonium or substituted ammonium salts thereof having from 3 to 21 carbon atoms in the acid part, and(G) at least on alkylamine of the general formula (II)whereR4is an organic radical having from 6 to 10 carbon atoms, in particular an alkyl or alkenyl radical having from 6 to 10 carbon atoms, preferably from 7 to 9 and particularly preferably 8 carbon atoms, p and q are each, independently of one another, a positive integer from 1 to 20, preferably from 1 to 15, particularly preferably from 1 to 10, very particularly preferably from 1 to 5 and in particular from 1 to 3, and each Xj for i = 1 to p and 1 to q is selected independently from the group consisting of -CH2-CH2-O-, -CH2-CH(CH3)-O-, -CH(CH3)-CH2-O-, -CH2-C(CH3)2-O-, -C(CH3)2-CH2-O-, -CH2-CH(C2H5)-O-, -CH(C2H5)-CH2-O-, -CH(CH3)-CH(CH3)-O-, -CH2-CH2-CH2-O- and -CH2-CH2-CH2-CH2-O-, preferably selected from the group consisting of -CH2-CH2-O-, -CH2-CH(CH3)-O- and -CH(CH3)-CH2-O-, with particular preference being given to -CH2-CH2-O-.

2. Coolants according to Claim 1 , comprising(A) 45 to 65 wt% of at least one antifreezing agent,(B) 30 to 50 wt% water,(C1) 0.01 to 0.5 wt% of at least one 2-thiothiazole of the general formula (I),(C2) 0 to 0.75 wt% of at least one azol derivative different from (C1 ),(D) 0.01 to 0.75 wt% of at least one inorganic salt as further corrosion inhibitor,(E) 0 to 2 wt% at least one inorganic phosphate salt,(F) 0.1 to 2 wt% at least one aliphatic, cycloaliphatic or aromatic monocarboxylic, dicarboxylic or tricarboxylic acid, and(G) 0.5 to 2.0 wt% of at least on alkylamine of the general formula (II),(H) optionally other additives selected from the group consisting of defoamers, bitter substances, and hard water stabilisers, with the proviso that the sum of all components always add up to 100 wt%.

3. Coolants according to any one of the preceding claims, wherein the electrical conductivity according to ASTMD 1125 at 25 °C of the coolant as 50% aqueous solution is from 150 to 3000 piS / cm.

4. Coolants according to any one of the preceding claims, wherein the antifreezing agent (A) is selected from the group consisting of 1,2-ethylene glycol and 1,2-propylene glycol, preferably 1 ,2-ethylene glycol.

5. Coolants according to any one of the preceding claims, wherein the 2-thiothiazole of the general formula (I)(C1) is selected from the group consisting of (2-benzothiazylthio)acetic acid and 3-(2-benzothiazy lthio)propionic acid or an alkali metal, ammonium or substituted ammonium salt thereof.

6. Coolants according to any one of the preceding claims, wherein at least one azol derivative (C2) different from(C1) is present and is selected from the group consisting of benzotriazole, tolutriazole (tolyltriazole), and hydrogenated tolutriazole, preferably selected from the group consisting of benzotriazole and tolutriazole.

7. Coolants according to any one of the preceding claims, wherein the at least one inorganic salt (D) is selected from the group consisting of molybdates, borates, vanadates, and tungstates, preferably selected from the group consisting of molybdates, borates, and vanadates, more preferably selected from the group consisting of molybdates, borates, and vanadates, even more preferably are molybdates.

8. Coolants according to any one of the preceding claims, wherein at least one inorganic phosphate salt (E) is present.

9. Coolants according to any one of the preceding claims, wherein the at least one carboxylic acid comprises at least one aliphatic monocarboxylic acid, preferably selected from the group consisting of 2-ethylhexanoic acid, n-nonanoic acid (pelargonic acid), and isononanoic acid.

10. Coolants according to any one of the preceding claims, wherein the at least one carboxylic acid comprises at least one aliphatic dicarboxylic acid, preferably selected from the group consisting of adipic acid and decanedioic acid.11 . Coolants according to any one of the preceding claims, wherein a mixture of at least one aliphatic monocarboxylic acid and at least one aliphatic dicarboxylic acid is present.

12. Coolants according to any one of the preceding claims, wherein alkylamine (G) is selected from the group consisting of ethoxylated n-hexylamine, n-heptylamine, n-octylamine, 2-ethylhexylamine, n-nonylamine, and isononylamine, preferably selected from the group consisting of ethoxylated n-hexylamine, n-octylamine, and 2-ethylhexylamine, more preferably is ethoxylated n-octylamine.

13. Coolants according to Claim 12, wherein the degree of ethoxylation of the alkylamine is from 2 to 4, preferably from 2 to 3, and more preferably is 2.

14. Use of coolants according to any one of the preceding claims in cooling systems of vehicles with internal combustion engines, electric engines or hybrid engines.

15. Use according to Claim 14, wherein the cooling system is at least partly, preferably predominantly or solely made of aluminium or aluminium alloys.

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